Reduce Campus Greenhouse Gas Emissions to Net Zero

Green House Gas Icon


Accounting for campus growth, achieve carbon neutrality by 2046 — Princeton’s 300th anniversary — through the use of repeatable, scalable and innovative solutions.


Campus emissions (metric tons CO2 x 1000)

GHG Dashboard Graph

*Targets reflect CO2 equivalence (CO2e)

  • Baseline
  • Current Performance
  • Future Targets
  • Previous Targets

Global Context, Local Action

According to the Intergovernmental Panel on Climate Change, humanity now experiences the consequences of 1°C of average planetary warming, including rising sea levels and more extreme weather. While climate change affects all of the planet’s populations, those in developing countries and disadvantaged populations in all countries are even more vulnerable to climate impacts. Changes in human behavior at all scales are required to prevent the predicted catastrophic consequences of more than 1.5°C warming.1

Between 2005 and 2014, college campuses in the U.S. reduced their greenhouse gas emissions by more than 6 percent, with many institutions in the coastal Northeast region averaging a reduction of more than 16 percent.2 Princeton is also demonstrating significant reductions in emissions over time.

Short and Long Term Objectives

Princeton’s new target is to reach net zero campus greenhouse gas emissions — reducing both direct emissions from on-site energy production and fleet fuel use, and indirect emissions from purchased electricity — by 2046. Additional indirect emissions from commuting, procurement and other activities will be tracked and reduced where feasible.

Our pathway to carbon neutrality relies on both known and unknown strategies, spanning new on-site energy infrastructure, the potential purchase of new renewable electricity generation off-site, and changes in everyday behavior across the campus community.

Princeton’s Progress To Date

Since 2008, Princeton’s efforts to reduce campus carbon dioxide emissions to 1990 levels by 2020 (without the purchase of market offsets) have been very successful. Even after adding 2 million gross square feet of built space since 1990, the University has achieved an 11 percent absolute reduction from 2008 greenhouse gas levels as of this past year. While the institution had set a goal to reduce emissions to 1990 levels, or by 15 percent, by 2020, COVID-19 requirements resulted in elevated energy use from increased air flows in buildings. With the assumption that air flows will revert to pre-pandemic levels in the future, we are now looking ahead to achieving our 2026 target. 

Notable contributions to that progress include the development of campus “Greenhouse Gas Reduction Decision-Making Criteria” by a faculty-led CO2 Task Force, improved central plant efficiencies, installation of ground source heat pump (geoexchange) systems, a $45 million investment in existing building energy-efficiency improvements with a collective five-year-or-less payback, and the potential claim around 2020 of carbon emissions reduction from our 4.5-megawatt on-campus photovoltaic array.

However, while our campus systems are highly efficient, we continue to combust fossil fuels (natural gas) as our primary energy source — a practice we will transition away from as we strive for net zero campus emissions. The strategies identified below set the stage for that transition.

Annual Campus Greenhouse Gas Emissions and Campus Square Footage

GHG emissions footage graph

*Represents all buildings that are connected to the main campus utility systems, including power purchased from the regional grid. Also included are off-campus buildings that house significant energy-consuming programs, including Lakeside Apartments, 701 Carnegie Center and the High-Performance Computing Research Center, as well as emissions from Athletics and Facilities fleet vehicles. The reported gross square footage of building area reflects those included in the greenhouse emissions inventory, verified to capture the vast majority of campus emissions.

Decision-Making Criteria

In 2015, the University’s faculty-led CO2 Task Force recommended the following criteria to guide greenhouse gas reduction decisions. Since then, these criteria have been integrated with campus and infrastructure master planning, as well as operational planning.

  • Establish a clear pathway to carbon emissions neutrality by 2046 (Princeton’s 300th anniversary).
  • Adopt a self-imposed greenhouse gas emissions budget of approximately 1,750,000 tons of CO2e, representing the total net emissions that are allowed from on-campus (scope 1 and 2) operations from now into the indefinite future.
  • Greenhouse gases have a cumulative impact on climate and we recommend against postponing reductions due to the expectation of new future technologies. Steady reductions in annual greenhouse gas emissions between now and 2046 should occur, though the actual reduction curve may not be linear.
  • By 2046 obtain carbon neutrality in a scalable fashion that is compatible with a dramatic nation-wide reduction in greenhouse gas emissions. In future campus development, all projects should answer the question, “Will today’s decision facilitate a movement towards the objective of nationwide decarbonization?”
  • Princeton’s current policy is to reduce on-campus emissions without the purchase of offsets of any kind. Maintain the rationale that paying others so we can continue to pollute is not an effective global solution to climate change. However, if necessary to reach carbon neutrality, off-campus initiatives which reduce emissions may be allowable as long as they are additional to anything already in place, are independently verifiable, and ultimately will contribute to a globally scalable greenhouse gas mitigation strategy. Consideration of netnegative carbon emissions technologies is possible.
  • Adopt both technical and behavioral solutions to achieve greenhouse gas emission neutrality.
  • Strive to coordinate academic research and teaching with carbon neutrality goals, including using the campus as a laboratory for new technologies and approaches. Initiatives to help spur innovation and leverage the University’s research prowess, educational mission and student/alumni network could lead to important breakthroughs.
  • Facilitate replication of successful greenhouse gas mitigation approaches. Communication of Princeton’s initiatives to students, alumni and the public should be emphasized.

Campus Action Items

  • Convert from natural gas-fueled campus steam production to a heating hot water system with geoexchange wells and heat pumps.
  • Renew allocation of $50 million in energy-efficiency improvements for existing buildings.
  • Expand solar power generation on campus, and evaluate off-campus renewable electricity options that meet our decision-making criteria.
  • Track and reduce key indirect greenhouse gas emissions sources (Scope 3 emissions).
  • Investigate long-term fuel alternatives that verifiably contribute to a fossil-free future.
  • Re-evaluate our greenhouse gas emissions inventory (Scope 1 and 2) to assure that all significant sources of campus-based emissions are included.
  • Align effective practices to reduce indirect and direct greenhouse gas emissions across campus through coordinated departmental action plans.
  • Advance evidence-based greenhouse gas emissions reduction solutions by continuing to actively engage students and faculty to serve on advisory committees and by supporting campus-as-lab research endeavors.
  • Reinforce Princeton’s climate action objectives during key programs, including but not limited to orientation for all students, faculty and staff; campus tours; Princeton Preview for undergraduates; visiting weekends for graduate students; residential life and campus dining; athletics; Reunions and other events.
  • Apply behavioral science approaches to promote widespread adoption of mindful energy-use behaviors, through programs, building design and other methods.
  • Scale action beyond Princeton through partnerships, such as the International District Energy Association and the Microgrid Resources Coalition, which was co-founded with multiple partners by Princeton’s Facilities’ Engineering and Campus Energy department.
Scales of Impact - You/Campus

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Anticipated CO2e Reduction Strategies

2026 Target

Reduce campus greenhouse gas emissions to 73,000 metric tons CO2e irrespective of growth and without the purchase of market offsets.

2046 Target

Net zero campus greenhouse gas emissions per year.

GHG Reduction Strategies

*Biofuels require rigorous study to be confirmed as verifiable sustainable alternatives to fossil fuels.